Complex shape steerable tissue visualization and manipulation catheter

ABSTRACT

Complex shape steerable tissue visualization and manipulation catheters and their methods of use of disclosed herein. The deployment catheter may be articulated utilizing various steering mechanisms to adjust a position of a visualization hood or membrane through which underlying tissue may be visualized.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of priority to U.S. Prov. Pat. App.60/914,648 filed Apr. 27, 2007, which is incorporated herein byreference in its entirety.

FIELD OF THE INVENTION

The present invention relates generally to catheters having imaging andmanipulation features for intravascularly accessing regions of the body.

BACKGROUND OF THE INVENTION

Conventional devices for accessing and visualizing interior regions of abody lumen are known. For example, ultrasound devices have been used toproduce images from within a body in vivo. Ultrasound has been used bothwith and without contrast agents, which typically enhanceultrasound-derived images.

Other conventional methods have utilized catheters or probes havingposition sensors deployed within the body lumen, such as the interior ofa cardiac chamber. These types of positional sensors are typically usedto determine the movement of a cardiac tissue surface or the electricalactivity within the cardiac tissue. When a sufficient number of pointshave been sampled by the sensors, a “map” of the cardiac tissue may begenerated.

Another conventional device utilizes an inflatable balloon which istypically introduced intravascularly in a deflated state and theninflated against the tissue region to be examined. Imaging is typicallyaccomplished by an optical fiber or other apparatus such as electronicchips for viewing the tissue through the membrane(s) of the inflatedballoon. Moreover, the balloon must generally be inflated for imaging.Other conventional balloons utilize a cavity or depression formed at adistal end of the inflated balloon. This cavity or depression is pressedagainst the tissue to be examined and is flushed with a clear fluid toprovide a clear pathway through the blood.

However, such imaging balloons have many inherent disadvantages. Forinstance, such balloons generally require that the balloon be inflatedto a relatively large size which may undesirably displace surroundingtissue and interfere with fine positioning of the imaging system againstthe tissue. Moreover, the working area created by such inflatableballoons are generally cramped and limited in size. Furthermore,inflated balloons may be susceptible to pressure changes in thesurrounding fluid. For example, if the environment surrounding theinflated balloon undergoes pressure changes, e.g., during systolic anddiastolic pressure cycles in a beating heart, the constant pressurechange may affect the inflated balloon volume and its positioning toproduce unsteady or undesirable conditions for optimal tissue imaging.

Accordingly, these types of imaging modalities are generally unable toprovide desirable images useful for sufficient diagnosis and therapy ofthe endoluminal structure, due in part to factors such as dynamic forcesgenerated by the natural movement of the heart. Moreover, anatomicstructures within the body can occlude or obstruct the image acquisitionprocess. Also, the presence and movement of opaque bodily fluids such asblood generally make in vivo imaging of tissue regions within the heartdifficult.

Other external imaging modalities are also conventionally utilized. Forexample, computed tomography (CT) and magnetic resonance imaging (MRI)are typical modalities which are widely used to obtain images of bodylumens such as the interior chambers of the heart. However, such imagingmodalities fail to provide real-time imaging for intra-operativetherapeutic procedures. Fluoroscopic imaging, for instance, is widelyused to identify anatomic landmarks within the heart and other regionsof the body. However, fluoroscopy fails to provide an accurate image ofthe tissue quality or surface and also fails to provide forinstrumentation for performing tissue manipulation or other therapeuticprocedures upon the visualized tissue regions. In addition, fluoroscopyprovides a shadow of the intervening tissue onto a plate or sensor whenit may be desirable to view the intraluminal surface of the tissue todiagnose pathologies or to perform some form of therapy on it.

Moreover, many of the conventional imaging systems lack the capabilityto provide therapeutic treatments or are difficult to manipulate inproviding effective therapies. For instance, the treatment in apatient's heart for atrial fibrillation is generally made difficult by anumber of factors, such as visualization of the target tissue, access tothe target tissue, and instrument articulation and management, amongstothers.

Conventional catheter techniques and devices, for example such as thosedescribed in U.S. Pat. Nos. 5,895,417; 5,941,845; and 6,129,724, used onthe epicardial surface of the heart may be difficult in assuring atransmural lesion or complete blockage of electrical signals. Inaddition, current devices may have difficulty dealing with varyingthickness of tissue through which a transmural lesion is desired.

Conventional accompanying imaging devices, such as fluoroscopy, areunable to detect perpendicular electrode orientation, catheter movementduring the cardiac cycle, and image catheter position throughout lesionformation. Without real-time visualization, it is difficult toreposition devices to another area that requires transmural lesionablation. The absence of real-time visualization also poses the risk ofincorrect placement and ablation of critical structures such as sinusnode tissue which can lead to fatal consequences.

BRIEF SUMMARY OF THE INVENTION

A tissue imaging system which is able to provide real-time in vivoaccess to and images of tissue regions within body lumens such as theheart through opaque media such as blood and which also providesinstruments for therapeutic procedures is provided by the invention.

The tissue-imaging apparatus relates to embodiments of a device andmethod to provide real-time images in vivo of tissue regions within abody lumen such as a heart, which is filled with blood flowingdynamically through it. Such an apparatus may be utilized for manyprocedures, e.g., mitral valvuloplasty, left atrial appendage closure,arrhythmia ablation (such as treatment for atrial fibrillation),transseptal access and patent foramen ovale closure among otherprocedures. Further details of such a visualization catheter and methodsof use are shown and described in U.S. Pat. Pub. 2006/0184048 A1, whichis incorporated herein by reference in its entirety.

Generally, the embodiments of a tissue imaging and manipulation devicedepicted in the present invention meet the challenge and solve theproblem of accessing regions of the body which are typically difficultto access. The design and control of the catheter shaft and the distaltip of the device as disclosed here provide a device uniquely capable ofaccessing a region such as the human heart, which is a region not onlydifficult to access, but which also has continuous blood flow. The bloodflow provides a barrier to visualizing the local tissue, which in turnmakes any manipulation at the local tissue nearly impossible. The uniqueelements that form the catheter shaft and the distal tip of the device,including the separate control of the shaft and tip and several optionalmodes of manipulation of either or both, provide for a device adaptableto addressing the challenges inherent in intravascular access andmanipulation of heart tissue, and for accomplishing a procedure in anyother difficult-to-access region in the body which is bathed in a mediumthat interfers with visualization.

Blood is continuously flowing through the heart at all times, and assuch presents a challenge to direct visualization and subsequentmanipulation of heart tissue. The tissue imaging and manipulationapparatus can comprise a delivery catheter or sheath through which adeployment catheter and imaging hood may be advanced for placementagainst or adjacent to the tissue to be imaged. The deployment cathetercan have a fluid delivery lumen through it as well as an imaging lumenwithin which an optical imaging fiber or electronic imaging assembly maybe disposed for imaging tissue. The distal tip of the device is anarticulatable tip connected to the catheter shaft, when deployed, theimaging hood within the articulatable tip may be expanded into anynumber of shapes, e.g., cylindrical, conical as shown, semi-spherical,etc., provided that an open area or field is defined by the imaginghood. The open area of the articulatable tip is the area within whichthe tissue region of interest may be imaged. The imaging hood may alsodefine an atraumatic contact lip or edge for placement or abutmentagainst the tissue surface in the region of interest. The distal end ofthe deployment catheter or separate manipulatable catheters within adelivery sheath may be articulated through various controllingmechanisms such as push-pull wires manually or via computer control.

The visualization catheter may also have one or more membranes or layersof a polymeric material which covers at least a portion of the openarea. The membrane or layer may be an extension of the deployed hood orit may be a separate structure. In either case, the membrane or layermay define at least one opening which allows for fluid communicationbetween the visualization hood and the fluid environment within whichthe catheter is immersed.

In operation, after the imaging hood (at the articulatable tip) has beendeployed, fluid may be pumped at a positive pressure through the fluiddelivery lumen (within the catheter) until the fluid fills the open areacompletely and displaces any blood from within the open area. When thehood and membrane or layer is pressed against the tissue region to bevisualized or treated, the contact between the one or more openings andthe tissue surface may help to retain the clear fluid within the hoodfor visualization. Moreover, the membrane or layer may help to retainthe fluid within the hood while also minimizing any fluid leakagetherefrom. Additionally, the one or more openings may also provide fordirect access to the underlying tissue region to be treated by anynumber of tools or instruments positioned within the hood at thearticulatable tip.

The fluid may comprise any biocompatible fluid, e.g., saline, water,plasma, Fluorinert™, etc., which is sufficiently transparent to allowfor relatively undistorted visualization through the fluid. The fluidmay be pumped continuously or intermittently to allow for image captureby an optional processor which may be in communication with theassembly.

The imaging hood may be deployed into an expanded shape and retractedwithin a catheter utilizing various mechanisms. Moreover, an imagingelement, such as a CCD/CMOS imaging camera, may be positioned distallyor proximally of the imaging hood when collapsed into its low-profileconfiguration. Such a configuration may reduce or eliminate frictionduring deployment and retraction as well as increase the available spacewithin the catheter not only for the imaging unit but also for the hood.

In further controlling the flow of the purging fluid within the hood,various measures may be taken in configuring the assembly to allow forthe infusion and controlled retention of the clearing fluid into thehood. By controlling the infusion and retention of the clearing fluid,the introduction of the clearing fluid into the patient body may belimited and the clarity of the imaging of the underlying tissue throughthe fluid within the hood may be maintained for relatively longerperiods of time by inhibiting, delaying, or preventing the infusion ofsurrounding blood into the viewing field.

Accordingly, there is provided here a device for visualization andmanipulation of difficult-to-reach tissue surfaces in a region of a bodyhaving a continuous interfering blood flow comprising a steerablecatheter shaft having controls for steering of the shaft in multipleplanes. The steering of the catheter and/or sheath are may be separatelycontrolled during a procedure so that a proximal steerable section of acatheter shaft can be steered to a target region without manipulation ofthe distal steerable section. Upon arrival at the target region, slightadjustments and steering of the hood may be articulated (and/orindependently) to address the tissue surface or otherwise contact orapproach a tissue surface.

The tasks performed by the articulatable hood utilize movement of thecatheter shaft, but the movements of the hood and the shaft can beindependent in function and control. For example, in order for the hoodto contact the tissue surface to flush the region in preparation forimaging, or for making contact with and manipulating the tissue (e.g.forming a lesion around a pulmonary ostium and the like), the cathetershaft may be moved and directed or re-directed and position the hood,then once the catheter shaft has placed the hood in a desirableposition, further articulation and control of the hood for cutting orlesion-formation or the like can occur. For example, the hood can bearticulated to contact the tissue surface and form a suitable seal inorder to flush the surface with saline to visualize the tissue at thesurface. The hood may have a conforming lip that can be used to makecontact with the tissue surface to facilitate any of these tasks ormanipulations. At the point where the hood is negotiating its positionat the tissue surface, any subsequent adjustments that may need to bemade to the positioning of the shaft can be made independently of themovement of the hood, although, where catheter shaft adjustment canfacilitate the hood's position relative to the tissue surface, the twocontrol mechanisms can work in concert with each other.

The catheter shaft may have one of a region of locking units on theshaft, the locking units comprising an ability to move multipledirections, e.g., four way steering. The catheter shaft might also havea separate region of locking units on the shaft proximal to the regionof locking units that move four ways, the proximal region of lockingunits capable of bending only in a single plane. The locking units canbe selected from pin links, bump links, ring links, one-way links andfour-way links

The distal articulatable hood can comprise one or more articulatableunits along the hood that are adapted to distal control and that allowthe hood to conform to the tissue surface. The articulatable units cancomprise multiple steerable leaflets inside a cone-like hood. Anarticulatable unit can comprise a steerable hood. It may also comprisecontrol members within the hood that allow the practitioner tomanipulate the lip that surrounds the hood and the like. The distalarticulatable hood can comprise a conforming lip that can be passivelysteered to contact the tissue surface.

The device can further comprise two or more variations in durometeralong the catheter shaft. For example, where there is at least onevariation in durometer along the catheter shaft, the variation indurometer can comprise a region of increased flexibility distal to aregion of relatively reduced flexibility, so that the distal most end ismore flexible and manipulatable.

Where the catheter shaft comprises locking units, the shaft can furthercomprise an outer sheath to smooth out links in the catheter shaft inthe region of the shaft having the locking units.

The catheter shaft can be multi-lumen and comprise multiple pull wires,each pull wire having its own separate access lumen within the cathetershaft. In addition, the device can have a fixed bend sheath over aportion of the catheter shaft to limit the movement of the shaft wherethe sheath is, and define a fixed angle of direction of the shaft at thefixed bend.

A tissue visualization unit adapted to visualizing accessed tissue canbe positioned within the articulatable tip. A tissue manipulation unitadapted to manipulating accessed tissue can likewise be positionedwithin the articulatable tip. A device can have both such units, foroptimally imaging and manipulating in the body during a procedure inreal time.

The invention is also a system for intravascularly accessing difficultto access target tissue in a region of the body having continuousinterfering blood flow. The system employs a device adapted tovisualization and manipulation of the accessed target tissue as justdescribed. The device for the system may have a catheter capable offlushing the target tissue surface at the distal tip so thatvisualization and manipulation at the surface can occur once the tip isin contact with the tissue surface, and both a unit for visualizing thetissue surface and manipulating tissue at the tissue surface positionedwithin the articulatable tip. Alternatively, the system can be just forvisualization of the tissue surface, in which case it will only have thevisualization mechanism.

The invention also contemplates a method of visualizing or manipulatingdifficult-to-access target tissue in a region of a body havingcontinuous interfering blood flow. The method comprises introducing intoa main artery in a patient a device such as just described having thesteerable catheter component and the distal attached articulatable tipcomponent. The controls for the catheter shaft include pull wires,locking units and variations in durometer of the shaft. Thearticulatable hood is expandable upon arrival of the device at a targetregion in a body, and the hood is capable of expansion to a greaterdiameter than the catheter shaft. The other elements and capabilities ofthe shaft and the hood apply to the device in its use in the method. Inuse, the device is navigated to a difficult-to-access region and targettissue surface, the catheter is steered using one or more controls onpull wires effecting multiple planar curvature of the catheter shaft asneeded to more specifically access the target tissue. The catheter shaftmight also be steered by virtue of the locking units on the shaft, forexample the 4-way locking units provide an opportunity to turn and twistthe shaft in several planes. The one-way locking units provide motion,but fix it in one plane. In addition to controlling the shaft, separatecontrol is exerted on the tip to conform the tip to the target tissuesurface, and clear a field at the target tissue surface for visualizingor manipulating the tissue at the surface. Flushing the region withfluid and conforming the tip to the surface of the target tissue canensue.

Manipulating the tissue in the practice of the method can comprise aprocedure selected from mitral valvuloplasty, left atrial appendageclosure, arrhythmia ablation, transeptal access, and patent formen ovaleclosure. Of particular interest is ablation of tissue around thepulmonary ostia, which is a way to treat atrial fibrillation. Theendocardium can be visualized in the method.

Typically, the complex manipulations will target the heart tissue, andcan be such tasks as pulmonary ostia ablation which treats atrialfibrillation. The device comprises a steerable catheter shaft havingcontrol for steering of the shaft in multiple planes. The catheter shaftwill typically have a proximal region of locking units on the shaftcapable of providing uni-directional movement of the catheter shaft inthat region, and a distal region of locking units on the shaft capableof providing 4-way directional movement of the catheter shaft in thatdistal region. The catheter shaft is also connected to a distalarticulatable tip expandable upon arrival of the device at the tissuesurface, the tip capable of expansion to a greater diameter than thecatheter shaft, the tip adapted to conform to a target tissue surfacewithin the target region in the body upon articulation of the tip, andcapable of flushing the target tissue surface so that visualization andmanipulation at the surface can occur. In this device the manipulationscomprising articulation of the articulatable tip and steering of thesteerable catheter are separately controlled during a procedure. Inorder to address atrial fibrillation, at the left atrium in the heart,the tissue surface of that is the ostia of the pulmonary veins isaccessed, and tissue surrounding these ostia is ablated by manipulatingthe articulatable tip of the catheter.

A procedure comprising forming lesions around a tissue surfacecomprising ostia of pulmonary veins in a left atrium is accomplished byintroducing a device in a femoral artery and directing it to the heart,the device comprising the elements of the device just described. Thearticulatable tip of the device may be adapted to conform to one at atime to an ostium of the pulmonary vein of the left atrium, the tip willbe capable of flushing the tissue surface of the ostium so thatvisualization and manipulation at the surface can occur. Manipulationscomprising articulation of the articulatable tip and steering of thesteerable catheter will be separately controlled during the atrialfibrillation treatment procedure. Such maneuvers as positioning the tipat a first ostium and purging charged saline at the tissue surface toform lesions around the ostium by steering the tip around the firstostium, and positioning the tip at a second ostium and purging chargedsaline at the tissue surface to form lesions around the ostium bysteering the tip around the second ostium, can be conducted toaccomplish a treatment directed to atrial fibrillation.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A shows a side view of one variation of a tissue imaging apparatusduring deployment from a sheath or delivery catheter.

FIG. 1B shows the deployed tissue imaging apparatus of FIG. 1A having anoptionally expandable hood or sheath attached to an imaging and/ordiagnostic catheter.

FIG. 1C shows an end view of a deployed imaging apparatus.

FIGS. 1D to 1F show the apparatus of FIGS. 1A to 1C with an additionallumen, e.g., for passage of a guidewire therethrough.

FIGS. 2A and 2B show one example of a deployed tissue imager positionedagainst or adjacent to the tissue to be imaged and a flow of fluid, suchas saline, displacing blood from within the expandable hood.

FIG. 3A shows an articulatable imaging assembly which may be manipulatedvia push-pull wires or by computer control.

FIGS. 3B and 3C show steerable instruments, respectively, where anarticulatable delivery catheter may be steered within the imaging hoodor a distal portion of the deployment catheter itself may be steered.

FIGS. 4A to 4C show side and cross-sectional end views, respectively, ofanother variation having an off-axis imaging capability.

FIGS. 4D and 4E show examples of various visualization imagers which maybe utilized within or along the imaging hood.

FIG. 5 shows an illustrative view of an example of a tissue imageradvanced intravascularly within a heart for imaging tissue regionswithin an atrial chamber.

FIGS. 6A to 6C illustrate deployment catheters having one or moreoptional inflatable balloons or anchors for stabilizing the deviceduring a procedure.

FIGS. 7A and 7B illustrate a variation of an anchoring mechanism such asa helical tissue piercing device for temporarily stabilizing the imaginghood relative to a tissue surface.

FIG. 7C shows another variation for anchoring the imaging hood havingone or more tubular support members integrated with the imaging hood;each support members may define a lumen therethrough for advancing ahelical tissue anchor within.

FIG. 8A shows an illustrative example of one variation of how a tissueimager may be utilized with an imaging device.

FIG. 8B shows a further illustration of a hand-held variation of thefluid delivery and tissue manipulation system.

FIGS. 9A to 9C illustrate an example of capturing several images of thetissue at multiple regions.

FIGS. 10A and 10B show charts illustrating how fluid pressure within theimaging hood may be coordinated with the surrounding blood pressure; thefluid pressure in the imaging hood may be coordinated with the bloodpressure or it may be regulated based upon pressure feedback from theblood.

FIG. 11A shows a perspective view of a variation of the tissuevisualization catheter with a steerable distal portion.

FIG. 11B shows the side view of the same device controlled by a singlepull wire.

FIG. 11C shows the side view of the same device with the pull wiretensioned to steer the steerable segment into a curved configuration.

FIG. 11D shows the perspective views of the same device illustratingarticulating and torquing motions to steer the hood into differentpositions.

FIG. 12A shows the side view of another variation of the steerabletissue visualization catheter with two pull wires.

FIG. 12B shows the side view of the same device with the right proximalpull wire tensioned.

FIG. 12C shows the side view of the same device with the left distalpull wire tensioned to create a double curve section along the steerablesegment of the catheter.

FIG. 12D shows the side view of the same device positioned againsttissue at an angle, e.g., perpendicularly, within a tight lumen orspace.

FIG. 13A shows the side view of a variation of the steerable tissuevisualization catheter with 4 pull wires.

FIG. 13B shows the side view of the same device configured into a doublebend defined by curve A and curve B.

FIG. 13C shows the side view of the same device configured into a doublebend defined by curve A and curve B in a direction opposite to thatshown in FIG. 13B.

FIG. 13D shows the side view of the same device doing a retroflex bendwhen both curve A and curve B are curved along the same side.

FIG. 13E shows the side view of the same device prior to placementagainst a tissue surface.

FIG. 13F shows the side view of the same device pressed against thetissue surface.

FIG. 13G shows the side view of the same device pressed against thetissue surface by reducing curvature of curves A and B.

FIG. 14A shows the perspective view of a variation of the tissuevisualization catheter with multiple pull wires to articulate hood inmultiple directions without the need to torque the catheter.

FIG. 14B shows the perspective view of the same device with hoodarticulatable in multiple directions.

FIG. 14C shows the perspective view of the same device with hoodarticulatable in multiple directions.

FIG. 14D shows the perspective view of the same device with hoodarticulatable in multiple directions.

FIG. 14E shows the perspective view of the same device with hoodarticulatable in multiple directions.

FIG. 15A shows the perspective view of a variation of the tissuevisualization catheter with serially aligned multiple links which aresteerable.

FIG. 15B shows the perspective view of a contoured link, e.g., bumplink.

FIG. 15C shows the perspective view of a plurality of links connected inseries together.

FIG. 15D shows the front view of the same device with steerable linksaligned linearly.

FIG. 15E shows the side view of the same device with steerable linksaligned into a double bend configuration.

FIG. 15F shows the side view of the same device showing steerable linksaligned to make tight bend radius to retroflex the hood.

FIG. 16A shows the side view of a variation of the tissue visualizationcatheter with steerable pinned links.

FIG. 16B shows the close up side view of pinned links.

FIG. 17A shows the side view of a variation of the tissue visualizationcatheter with steerable ring links.

FIG. 17B shows the close up side view of ring links.

FIG. 18 shows the side view of a variation of the tissue visualizationcatheter with the steerable section made from a laser-cut shaft.

FIG. 19A shows the top view of a steerable tissue visualization catheterwith steerable segment made up of a ribbed spine, e.g., “fish bone”shaped.

FIG. 19B illustrates a detail perspective view of a portion of thesteerable segment with one or more pull wires extending therethrough.

FIG. 20A shows the perspective view of a steerable tissue visualizationcatheter with slit tube as the steerable segment.

FIG. 20B shows the side view of the same device.

FIG. 20C shows the close up side view of the slit tube.

FIG. 21A shows a perspective view of a variation of a steerable tissuevisualization catheter with the steerable segment made from extrusion ofdiffering durometer.

FIG. 21B shows the side view of the same device where the steerablesegment is of a relatively flexible material.

FIG. 22A shows the side view of a variation of the tissue visualizationcatheter with a double bend steerable segment telescoping from apre-bent introducer sheath.

FIG. 22B shows the double bend steering by combining a passive pre-bentsheath with an actively articulated single bend steering catheter.

FIG. 22C shows the retroflex steering by combining a passive pre-bentsheath with an actively articulated single bend steering catheter.

FIG. 22D illustrates the ability to steer the hood to contact tissuewalls at tight angles through the interaction of the pre-bent sheath incombination with double bend steering on the catheter.

FIG. 22E shows the ability to steer and push tissue through tight anglesthrough the interaction of the pre-bent sheath in combination withdouble bend steering on the catheter.

FIG. 22F shows the ability to rotate and position a curved deploymentcatheter in a different plane with respect to the curved sheath.

FIG. 23A shows a side view of a pre-bent tissue visualization catheterwith a pre-bent introducer sheath.

FIG. 23B shows the side view of the visualization catheter andintroducer sheath with pre-bent curves aligned in the same direction andplane to steer the hood across a relatively wide angle.

FIG. 23C shows the side view of the same system with both pre-bendcurves in the same plane but rotated in opposite directions relative toone another.

FIG. 23D illustrates a perspective view of the same system with bothpre-bent curves in different planes relative to one another.

FIG. 24A shows a side view of a steerable tissue visualization catheterwith an active steerable sheath.

FIG. 24B shows a perspective view of the same system in the left atriumwith the sheath providing an initial curvature which defines atrajectory through which the deployment catheter may be advanced towardsthe target tissue; the deployment catheter itself may then be finelysteered to direct the hood against the target tissue to be treated.

FIG. 25A shows a side view of a steerable hood of the tissuevisualization catheter with multiple steerable leaflets.

FIG. 25B shows a side view of a steerable hood having multiple steeringleaflets actuated to steer the hood into an angled configurationrelative to a longitudinal axis of the deployment catheter

FIG. 25C illustrates a side view of the hood angled relative to thedeployment catheter positioned against a tissue surface.

FIG. 26A shows a perspective view of the tissue visualization catheterwith steerable hood.

FIG. 26B shows a side view of the same device.

FIG. 27A shows a perspective view of a tissue visualization catheterwith conforming lip at a distal end of the hood.

FIG. 27B shows a side view of the same device advanced towards a tissuesurface at an angle defined by the steerable introducer sheath.

FIG. 27C illustrates the hood pressed against the targeted tissue withthe lip conforming against the anatomy of the tissue.

FIG. 28 shows a perspective assembly view of the steerable section of acatheter having a distal section with connected links configured toallow for multi-directional articulation, e.g., four-way articulation,and a proximal section with connected links configured to allow forarticulation within a single plane, e.g., one-way articulation.

FIG. 29A illustrates a perspective detail view of the multi-directionalarticulation of the distal section of the steerable segment.

FIG. 29B illustrates a perspective detail view of articulation within asingle plane of a proximal section of the steerable segment.

FIG. 30A to 30C illustrates a device positioned within the left atriumwith the proximal steering section articulated within a single plane toretroflex the distal end and the distal steering section articulated tocircumscribe the ostium of the left superior pulmonary vein for ablationtreatment.

FIGS. 30D to 30F illustrates a device repositioned within the leftatrium to allow the distal steering section to circumscribe the ostiumof the right superior pulmonary vein for ablation treatment.

DETAILED DESCRIPTION OF THE INVENTION

Various exemplary embodiments of the invention are described below.Reference is made to these examples in a non-limiting sense. They areprovided to illustrate more broadly applicable aspects of the presentinvention. Various changes may be made to the invention described andequivalents may be substituted without departing from the true spiritand scope of the invention. In addition, many modifications may be madeto adapt a particular situation, material, composition of matter,process, process act(s) or step(s) to the objective(s), spirit or scopeof the present invention. All such modifications are intended to bewithin the scope of the claims made herein.

The tissue-imaging and manipulation apparatus of the invention is ableto provide real-time images in vivo of tissue regions within a bodylumen such as a heart, which are filled with blood flowing dynamicallythrough the region. The apparatus is also able to provide intravasculartools and instruments for performing various procedures upon the imagedtissue regions. Such an apparatus may be utilized for many procedures,e.g., facilitating transseptal access to the left atrium, cannulatingthe coronary sinus, diagnosis of valve regurgitation/stenosis,valvuloplasty, atrial appendage closure, arrhythmogenic focus ablation(such as for treating atrial fibrulation), among other procedures.Disclosure and information regarding tissue visualization cathetersgenerally which can be applied to the invention are shown and describedin further detail in commonly owned U.S. patent application Ser. No.11/259,498 filed Oct. 25, 2005, and published as 2006/0184048, which isincorporated herein by reference in its entirety. The basic apparatusfor visualizing and manipulating tissue upon intravascular access to thetarget region are depicted in FIGS. 1-10. The specific details of theinvention that permit specific access to difficult-to-access regionssuch as regions in the heart are depicted in FIGS. 11 to 32. Specificembodiments depicting devices and methods for specific heart-basedtissue manipulations such as forming lesions around the pulmonary ostiaare shown in FIGS. 28 to 32.

One variation of a tissue access and imaging apparatus is shown in thedetail perspective views of FIGS. 1A to 1C. As shown in FIG. 1A, tissueimaging and manipulation assembly 10 may be delivered intravascularlythrough the patient's body in a low-profile configuration via a deliverycatheter or sheath 14. In the case of treating tissue, such as themitral valve located at the outflow tract of the left atrium of theheart, it is generally desirable to enter or access the left atriumwhile minimizing trauma to the patient. To non-operatively effect suchaccess, one conventional approach involves puncturing the intra-atrialseptum from the right atrial chamber to the left atrial chamber in aprocedure commonly called a transseptal procedure or septostomy. Forprocedures such as percutaneous valve repair and replacement,transseptal access to the left atrial chamber of the heart may allow forlarger devices to be introduced into the venous system than cangenerally be introduced percutaneously into the arterial system.

When the imaging and manipulation assembly 10 is ready to be utilizedfor imaging tissue, imaging hood 12 may be advanced relative to catheter14 and deployed from a distal opening of catheter 14, as shown by thearrow. Upon deployment, imaging hood 12 may be unconstrained to expandor open into a deployed imaging configuration, as shown in FIG. 1B.Imaging hood 12 may be fabricated from a variety of pliable orconformable biocompatible material including but not limited to, e.g.,polymeric, plastic, or woven materials. One example of a woven materialis Kevlar® (E. I. du Pont de Nemours, Wilmington, Del.), which is anaramid and which can be made into thin, e.g., less than 0.001 in.,materials which maintain enough integrity for such applicationsdescribed herein. Moreover, the imaging hood 12 may be fabricated from atranslucent or opaque material and in a variety of different colors tooptimize or attenuate any reflected lighting from surrounding fluids orstructures, i.e., anatomical or mechanical structures or instruments. Ineither case, imaging hood 12 may be fabricated into a uniform structureor a scaffold-supported structure, in which case a scaffold made of ashape memory alloy, such as Nitinol, or a spring steel, or plastic,etc., may be fabricated and covered with the polymeric, plastic, orwoven material. Hence, imaging hood 12 may comprise any of a widevariety of barriers or membrane structures, as may generally be used tolocalize displacement of blood or the like from a selected volume of abody lumen or heart chamber. In exemplary embodiments, a volume withinan inner surface 13 of imaging hood 12 will be significantly less than avolume of the hood 12 between inner surface 13 and outer surface 11.

Imaging hood 12 may be attached at interface 24 to a deployment catheter16 which may be translated independently of deployment catheter orsheath 14. Attachment of interface 24 may be accomplished through anynumber of conventional methods. Deployment catheter 16 may define afluid delivery lumen 18 as well as an imaging lumen 20 within which anoptical imaging fiber or assembly may be disposed for imaging tissue.When deployed, imaging hood 12 may expand into any number of shapes,e.g., cylindrical, conical as shown, semi-spherical, etc., provided thatan open area or field 26 is defined by imaging hood 12. The open area 26is the area within which the tissue region of interest may be imaged.Imaging hood 12 may also define an atraumatic contact lip or edge 22 forplacement or abutment against the tissue region of interest. Moreover,the diameter of imaging hood 12 at its maximum fully deployed diameter,e.g., at contact lip or edge 22, is typically greater relative to adiameter of the deployment catheter 16 (although a diameter of contactlip or edge 22 may be made to have a smaller or equal diameter ofdeployment catheter 16). For instance, the contact edge diameter mayrange anywhere from 1 to 5 times (or even greater, as practicable) adiameter of deployment catheter 16. FIG. 1C shows an end view of theimaging hood 12 in its deployed configuration. Also shown are thecontact lip or edge 22 and fluid delivery lumen 18 and imaging lumen 20.

The imaging and manipulation assembly 10 may additionally define aguidewire lumen therethrough, e.g., a concentric or eccentric lumen, asshown in the side and end views, respectively, of FIGS. 1D to 1F. Thedeployment catheter 16 may define guidewire lumen 19 for facilitatingthe passage of the system over or along a guidewire 17, which may beadvanced intravascularly within a body lumen. The deployment catheter 16may then be advanced over the guidewire 17, as generally known in theart.

In operation, after imaging hood 12 has been deployed, as in FIG. 1B,and desirably positioned against the tissue region to be imaged alongcontact edge 22, the displacing fluid may be pumped at positive pressurethrough fluid delivery lumen 18 until the fluid fills open area 26completely and displaces any fluid 28 from within open area 26. Thedisplacing fluid flow may be laminarized to improve its clearing effectand to help prevent blood from re-entering the imaging hood 12.Alternatively, fluid flow may be started before the deployment takesplace. The displacing fluid, also described herein as imaging fluid, maycomprise any biocompatible fluid, e.g., saline, water, plasma, etc.,which is sufficiently transparent to allow for relatively undistortedvisualization through the fluid. Alternatively or additionally, anynumber of therapeutic drugs may be suspended within the fluid or maycomprise the fluid itself which is pumped into open area 26 and which issubsequently passed into and through the heart and the patient body.

As seen in the example of FIGS. 2A and 2B, deployment catheter 16 may bemanipulated to position deployed imaging hood 12 against or near theunderlying tissue region of interest to be imaged, in this example aportion of annulus A of mitral valve MV within the left atrial chamber.As the surrounding blood 30 flows around imaging hood 12 and within openarea 26 defined within imaging hood 12, as seen in FIG. 2A, theunderlying annulus A is obstructed by the opaque blood 30 and isdifficult to view through the imaging lumen 20. The translucent fluid28, such as saline, may then be pumped through fluid delivery lumen 18,intermittently or continuously, until the blood 30 is at leastpartially, and preferably completely, displaced from within open area 26by fluid 28, as shown in FIG. 2B.

Although contact edge 22 need not directly contact the underlyingtissue, it is at least preferably brought into close proximity to thetissue such that the flow of clear fluid 28 from open area 26 may bemaintained to inhibit significant backflow of blood 30 back into openarea 26. Contact edge 22 may also be made of a soft elastomeric materialsuch as certain soft grades of silicone or polyurethane, as typicallyknown, to help contact edge 22 conform to an uneven or rough underlyinganatomical tissue surface. Once the blood 30 has been displaced fromimaging hood 12, an image may then be viewed of the underlying tissuethrough the clear fluid 30. This image may then be recorded or availablefor real-time viewing for performing a therapeutic procedure. Thepositive flow of fluid 28 may be maintained continuously to provide forclear viewing of the underlying tissue. Alternatively, the fluid 28 maybe pumped temporarily or sporadically only until a clear view of thetissue is available to be imaged and recorded, at which point the fluidflow 28 may cease and blood 30 may be allowed to seep or flow back intoimaging hood 12. This process may be repeated a number of times at thesame tissue region or at multiple tissue regions.

In desirably positioning the assembly at various regions within thepatient body, a number of articulation and manipulation controls may beutilized. For example, as shown in the articulatable imaging assembly 40in FIG. 3A, one or more push-pull wires 42 may be routed throughdeployment catheter 16 for steering the distal end portion of the devicein various directions 46 to desirably position the imaging hood 12adjacent to a region of tissue to be visualized. Depending upon thepositioning and the number of push-pull wires 42 utilized, deploymentcatheter 16 and imaging hood 12 may be articulated into any number ofconfigurations 44. The push-pull wire or wires 42 may be articulated viatheir proximal ends from outside the patient body manually utilizing oneor more controls. Alternatively, deployment catheter 16 may bearticulated by computer control, as further described below.

Additionally or alternatively, an articulatable delivery catheter 48,which may be articulated via one or more push-pull wires and having animaging lumen and one or more working lumens, may be delivered throughthe deployment catheter 16 and into imaging hood 12. With a distalportion of articulatable delivery catheter 48 within imaging hood 12,the clear displacing fluid may be pumped through delivery catheter 48 ordeployment catheter 16 to clear the field within imaging hood 12. Asshown in FIG. 3B, the articulatable delivery catheter 48 may bearticulated within the imaging hood to obtain a better image of tissueadjacent to the imaging hood 12. Moreover, articulatable deliverycatheter 48 may be articulated to direct an instrument or tool passedthrough the catheter 48, as described in detail below, to specific areasof tissue imaged through imaging hood 12 without having to repositiondeployment catheter 16 and re-clear the imaging field within hood 12.

Alternatively, rather than passing an articulatable delivery catheter 48through the deployment catheter 16, a distal portion of the deploymentcatheter 16 itself may comprise a distal end 49 which is articulatablewithin imaging hood 12, as shown in FIG. 3C. Directed imaging,instrument delivery, etc., may be accomplished directly through one ormore lumens within deployment catheter 16 to specific regions of theunderlying tissue imaged within imaging hood 12.

Visualization within the imaging hood 12 may be accomplished through animaging lumen 20 defined through deployment catheter 16, as describedabove. In such a configuration, visualization is available in astraight-line manner, i.e., images are generated from the field distallyalong a longitudinal axis defined by the deployment catheter 16.Alternatively or additionally, an articulatable imaging assembly havinga pivotable support member 50 may be connected to, mounted to, orotherwise passed through deployment catheter 16 to provide forvisualization off-axis relative to the longitudinal axis defined bydeployment catheter 16, as shown in FIG. 4A. Support member 50 may havean imaging element 52, e.g., a CCD or CMOS imager or optical fiber,attached at its distal end with its proximal end connected to deploymentcatheter 16 via a pivoting connection 54.

If one or more optical fibers are utilized for imaging, the opticalfibers 58 may be passed through deployment catheter 16, as shown in thecross-section of FIG. 4B, and routed through the support member 50. Theuse of optical fibers 58 may provide for increased diameter sizes of theone or several lumens 56 through deployment catheter 16 for the passageof diagnostic and/or therapeutic tools therethrough. Alternatively,electronic chips, such as a charge coupled device (CCD) or a CMOSimager, which are typically known, may be utilized in place of theoptical fibers 58, in which case the electronic imager may be positionedin the distal portion of the deployment catheter 16 with electric wiresbeing routed proximally through the deployment catheter 16.Alternatively, the electronic imagers may be wirelessly coupled to areceiver for the wireless transmission of images. Additional opticalfibers or light emitting diodes (LEDs) can be used to provide lightingfor the image or operative theater, as described below in furtherdetail. Support member 50 may be pivoted via connection 54 such that themember 50 can be positioned in a low-profile configuration withinchannel or groove 60 defined in a distal portion of catheter 16, asshown in the cross-section of FIG. 4C. During intravascular delivery ofdeployment catheter 16 through the patient body, support member 50 canbe positioned within channel or groove 60 with imaging hood 12 also inits low-profile configuration. During visualization, imaging hood 12 maybe expanded into its deployed configuration and support member 50 may bedeployed into its off-axis configuration for imaging the tissue adjacentto hood 12, as in FIG. 4A. Other configurations for support member 50for off-axis visualization may be utilized, as desired.

FIG. 4D shows a partial cross-sectional view of an example where one ormore optical fiber bundles 62 may be positioned within the catheter andwithin imaging hood 12 to provide direct in-line imaging of the openarea within hood 12. FIG. 4E shows another example where an imagingelement 64 (e.g., CCD or CMOS electronic imager) may be placed along aninterior surface of imaging hood 12 to provide imaging of the open areasuch that the imaging element 64 is off-axis relative to a longitudinalaxis of the hood 12. The off-axis position of element 64 may provide fordirect visualization and uninhibited access by instruments from thecatheter to the underlying tissue during treatment.

FIG. 5 shows an illustrative cross-sectional view of a heart H havingtissue regions of interest being viewed via an imaging assembly 10. Inthis example, delivery catheter assembly 70 may be introducedpercutaneously into the patient's vasculature and advanced through thesuperior vena cava SVC and into the right atrium RA. The deliverycatheter or sheath 72 may be articulated through the atrial septum ASand into the left atrium LA for viewing or treating the tissue, e.g.,the annulus A, surrounding the mitral valve MV. As shown, deploymentcatheter 16 and imaging hood 12 may be advanced out of delivery catheter72 and brought into contact or in proximity to the tissue region ofinterest. In other examples, delivery catheter assembly 70 may beadvanced through the inferior vena cava IVC, if so desired. Moreover,other regions of the heart H, e.g., the right ventricle RV or leftventricle LV, may also be accessed and imaged or treated by imagingassembly 10.

In accessing regions of the heart H or other parts of the body, thedelivery catheter or sheath 14 may comprise a conventionalintra-vascular catheter or an endoluminal delivery device.Alternatively, robotically-controlled delivery catheters may also beoptionally utilized with the imaging assembly described herein, in whichcase a computer-controller 74 may be used to control the articulationand positioning of the delivery catheter 14. An example of arobotically-controlled delivery catheter which may be utilized isdescribed in further detail in US Pat. Pub. 2002/0087169 A1 to Brock etal. entitled “Flexible Instrument”, which is incorporated herein byreference in its entirety. Other robotically-controlled deliverycatheters manufactured by Hansen Medical, Inc. (Mountain View, Calif.)may also be utilized with the delivery catheter 14.

To facilitate stabilization of the deployment catheter 16 during aprocedure, one or more inflatable balloons or anchors 76 may bepositioned along the length of catheter 16, as shown in FIG. 6A. Forexample, when utilizing a transseptal approach across the atrial septumAS into the left atrium LA, the inflatable balloons 76 may be inflatedfrom a low-profile into their expanded configuration to temporarilyanchor or stabilize the catheter 16 position relative to the heart H.FIG. 6B shows a first balloon 78 inflated while FIG. 6C also shows asecond balloon 80 inflated proximal to the first balloon 78. In such aconfiguration, the septal wall AS may be wedged or sandwiched betweenthe balloons 78, 80 to temporarily stabilize the catheter 16 and imaginghood 12. A single balloon 78 or both balloons 78, 80 may be used. Otheralternatives may utilize expandable mesh members, malecots, or any othertemporary expandable structure. After a procedure has been accomplished,the balloon assembly 76 may be deflated or re-configured into alow-profile for removal of the deployment catheter 16.

To further stabilize a position of the imaging hood 12 relative to atissue surface to be imaged, various anchoring mechanisms may beoptionally employed for temporarily holding the imaging hood 12 againstthe tissue. Such anchoring mechanisms may be particularly useful forimaging tissue which is subject to movement, e.g., when imaging tissuewithin the chambers of a beating heart. A tool delivery catheter 82having at least one instrument lumen and an optional visualization lumenmay be delivered through deployment catheter 16 and into an expandedimaging hood 12. As the imaging hood 12 is brought into contact againsta tissue surface T to be examined, anchoring mechanisms such as ahelical tissue piercing device 84 may be passed through the tooldelivery catheter 82, as shown in FIG. 7A, and into imaging hood 12.

The helical tissue engaging device 84 may be torqued from its proximalend outside the patient body to temporarily anchor itself into theunderlying tissue surface T. Once embedded within the tissue T, thehelical tissue engaging device 84 may be pulled proximally relative todeployment catheter 16 while the deployment catheter 16 and imaging hood12 are pushed distally, as indicated by the arrows in FIG. 7B, to gentlyforce the contact edge or lip 22 of imaging hood against the tissue T.The positioning of the tissue engaging device 84 may be lockedtemporarily relative to the deployment catheter 16 to ensure securepositioning of the imaging hood 12 during a diagnostic or therapeuticprocedure within the imaging hood 12. After a procedure, tissue engagingdevice 84 may be disengaged from the tissue by torquing its proximal endin the opposite direction to remove the anchor form the tissue T and thedeployment catheter 16 may be repositioned to another region of tissuewhere the anchoring process may be repeated or removed from the patientbody. The tissue engaging device 84 may also be constructed from otherknown tissue engaging devices such as vacuum-assisted engagement orgrasper-assisted engagement tools, among others.

Although a helical anchor 84 is shown, this is intended to beillustrative and other types of temporary anchors may be utilized, e.g.,hooked or barbed anchors, graspers, etc. Moreover, the tool deliverycatheter 82 may be omitted entirely and the anchoring device may bedelivered directly through a lumen defined through the deploymentcatheter 16.

In another variation where the tool delivery catheter 82 may be omittedentirely to temporarily anchor imaging hood 12, FIG. 7C shows an imaginghood 12 having one or more tubular support members 86, e.g., foursupport members 86 as shown, integrated with the imaging hood 12. Thetubular support members 86 may define lumens therethrough each havinghelical tissue engaging devices 88 positioned within. When an expandedimaging hood 12 is to be temporarily anchored to the tissue, the helicaltissue engaging devices 88 may be urged distally to extend from imaginghood 12 and each may be torqued from its proximal end to engage theunderlying tissue T. Each of the helical tissue engaging devices 88 maybe advanced through the length of deployment catheter 16 or they may bepositioned within tubular support members 86 during the delivery anddeployment of imaging hood 12. Once the procedure within imaging hood 12is finished, each of the tissue engaging devices 88 may be disengagedfrom the tissue and the imaging hood 12 may be repositioned to anotherregion of tissue or removed from the patient body.

An illustrative example is shown in FIG. 8A of a tissue imaging assemblyconnected to a fluid delivery system 90 and to an optional processor 98and image recorder and/or viewer 100. The fluid delivery system 90 maygenerally comprise a pump 92 and an optional valve 94 for controllingthe flow rate of the fluid into the system. A fluid reservoir 96,fluidly connected to pump 92, may hold the fluid to be pumped throughimaging hood 12. An optional central processing unit or processor 98 maybe in electrical communication with fluid delivery system 90 forcontrolling flow parameters such as the flow rate and/or velocity of thepumped fluid. The processor 98 may also be in electrical communicationwith an image recorder and/or viewer 100 for directly viewing the imagesof tissue received from within imaging hood 12. Imager recorder and/orviewer 100 may also be used not only to record the image but also thelocation of the viewed tissue region, if so desired.

Optionally, processor 98 may also be utilized to coordinate the fluidflow and the image capture. For instance, processor 98 may be programmedto provide for fluid flow from reservoir 96 until the tissue area hasbeen displaced of blood to obtain a clear image. Once the image has beendetermined to be sufficiently clear, either visually by a practitioneror by computer, an image of the tissue may be captured automatically byrecorder 100 and pump 92 may be automatically stopped or slowed byprocessor 98 to cease the fluid flow into the patient. Other variationsfor fluid delivery and image capture are, of course, possible and theaforementioned configuration is intended only to be illustrative and notlimiting.

FIG. 8B shows a further illustration of a hand-held variation of thefluid delivery and tissue manipulation system 110. In this variation,system 110 may have a housing or handle assembly 112 which can be heldor manipulated by the physician from outside the patient body. The fluidreservoir 114, shown in this variation as a syringe, can be fluidlycoupled to the handle assembly 112 and actuated via a pumping mechanism116, e.g., lead screw. Fluid reservoir 114 may be a simple reservoirseparated from the handle assembly 112 and fluidly coupled to handleassembly 112 via one or more tubes. The fluid flow rate and othermechanisms may be metered by the electronic controller 118.

Deployment of imaging hood 12 may be actuated by a hood deploymentswitch 120 located on the handle assembly 112 while dispensation of thefluid from reservoir 114 may be actuated by a fluid deployment switch122, which can be electrically coupled to the controller 118. Controller118 may also be electrically coupled to a wired or wireless antenna 124optionally integrated with the handle assembly 112, as shown in thefigure. The wireless antenna 124 can be used to wirelessly transmitimages captured from the imaging hood 12 to a receiver, e.g., viaBluetooth® wireless technology (Bluetooth SIG, Inc., Bellevue, Wash.),RF, etc., for viewing on a monitor 128 or for recording for laterviewing.

Articulation control of the deployment catheter 16, or a deliverycatheter or sheath 14 through which the deployment catheter 16 may bedelivered, may be accomplished by computer control, as described above,in which case an additional controller may be utilized with handleassembly 112. In the case of manual articulation, handle assembly 112may incorporate one or more articulation controls 126 for manualmanipulation of the position of deployment catheter 16. Handle assembly112 may also define one or more instrument ports 130 through which anumber of intravascular tools may be passed for tissue manipulation andtreatment within imaging hood 12, as described further below.Furthermore, in certain procedures, fluid or debris may be sucked intoimaging hood 12 for evacuation from the patient body by optionallyfluidly coupling a suction pump 132 to handle assembly 112 or directlyto deployment catheter 16.

As described above, fluid may be pumped continuously into imaging hood12 to provide for clear viewing of the underlying tissue. Alternatively,fluid may be pumped temporarily or sporadically only until a clear viewof the tissue is available to be imaged and recorded, at which point thefluid flow may cease and the blood may be allowed to seep or flow backinto imaging hood 12. FIGS. 9A to 9C illustrate an example of capturingseveral images of the tissue at multiple regions. Deployment catheter 16may be desirably positioned and imaging hood 12 deployed and broughtinto position against a region of tissue to be imaged, in this examplethe tissue surrounding a mitral valve MV within the left atrium of apatient's heart. The imaging hood 12 may be optionally anchored to thetissue, as described above, and then cleared by pumping the imagingfluid into the hood 12. Once sufficiently clear, the tissue may bevisualized and the image captured by control electronics 118. The firstcaptured image 140 may be stored and/or transmitted wirelessly 124 to amonitor 128 for viewing by the physician, as shown in FIG. 9A.

The deployment catheter 16 may be then repositioned to an adjacentportion of mitral valve MV, as shown in FIG. 9B, where the process maybe repeated to capture a second image 142 for viewing and/or recording.The deployment catheter 16 may again be repositioned to another regionof tissue, as shown in FIG. 9C, where a third image 144 may be capturedfor viewing and/or recording. This procedure may be repeated as manytimes as necessary for capturing a comprehensive image of the tissuesurrounding mitral valve MV, or any other tissue region. When thedeployment catheter 16 and imaging hood 12 is repositioned from tissueregion to tissue region, the pump may be stopped during positioning andblood or surrounding fluid may be allowed to enter within imaging hood12 until the tissue is to be imaged, where the imaging hood 12 may becleared, as above.

As mentioned above, when the imaging hood 12 is cleared by pumping theimaging fluid within for clearing the blood or other bodily fluid, thefluid may be pumped continuously to maintain the imaging fluid withinthe hood 12 at a positive pressure or it may be pumped under computercontrol for slowing or stopping the fluid flow into the hood 12 upondetection of various parameters or until a clear image of the underlyingtissue is obtained. The control electronics 118 may also be programmedto coordinate the fluid flow into the imaging hood 12 with variousphysical parameters to maintain a clear image within imaging hood 12.

One example is shown in FIG. 10A which shows a chart 150 illustratinghow fluid pressure within the imaging hood 12 may be coordinated withthe surrounding blood pressure. Chart 150 shows the cyclical bloodpressure 156 alternating between diastolic pressure 152 and systolicpressure 154 over time T due to the beating motion of the patient heart.The fluid pressure of the imaging fluid, indicated by plot 160, withinimaging hood 12 may be automatically timed to correspond to the bloodpressure changes 160 such that an increased pressure is maintainedwithin imaging hood 12 which is consistently above the blood pressure156 by a slight increase ΔP, as illustrated by the pressure differenceat the peak systolic pressure 158. This pressure difference, ΔP, may bemaintained within imaging hood 12 over the pressure variance of thesurrounding blood pressure to maintain a positive imaging fluid pressurewithin imaging hood 12 to maintain a clear view of the underlyingtissue. One benefit of maintaining a constant ΔP is a constant flow andmaintenance of a clear field.

FIG. 10B shows a chart 162 illustrating another variation formaintaining a clear view of the underlying tissue where one or moresensors within the imaging hood 12, as described in further detailbelow, may be configured to sense pressure changes within the imaginghood 12 and to correspondingly increase the imaging fluid pressurewithin imaging hood 12. This may result in a time delay, ΔT, asillustrated by the shifted fluid pressure 160 relative to the cyclingblood pressure 156, although the time delays ΔT may be negligible inmaintaining the clear image of the underlying tissue. Predictivesoftware algorithms can also be used to substantially eliminate thistime delay by predicting when the next pressure wave peak will arriveand by increasing the pressure ahead of the pressure wave's arrival byan amount of time equal to the aforementioned time delay to essentiallycancel the time delay out.

The variations in fluid pressure within imaging hood 12 may beaccomplished in part due to the nature of imaging hood 12. An inflatableballoon, which is conventionally utilized for imaging tissue, may beaffected by the surrounding blood pressure changes. On the other hand,an imaging hood 12 retains a constant volume therewithin and isstructurally unaffected by the surrounding blood pressure changes, thusallowing for pressure increases therewithin. The material that hood 12is made from may also contribute to the manner in which the pressure ismodulated within this hood 12. A stiffer hood material, such as highdurometer polyurethane or Nylon, may facilitate the maintaining of anopen hood when deployed. On the other hand, a relatively lower durometeror softer material, such as a low durometer PVC or polyurethane, maycollapse from the surrounding fluid pressure and may not adequatelymaintain a deployed or expanded hood.

In further controlling the flow of the purging fluid within the hood 12,various measures may be taken in configuring the assembly to allow forthe infusion and controlled retention of the clearing fluid into thehood. By controlling the infusion and retention of the clearing fluid,the introduction of the clearing fluid into the patient body may belimited and the clarity of the imaging of the underlying tissue throughthe fluid within the hood 12 may be maintained for relatively longerperiods of time by inhibiting, delaying, or preventing the infusion ofsurrounding blood into the viewing field.

In utilizing the hood 12 and various instruments through the hood fortissue treatment, hood 12 may be articulated in a variety ofconfigurations to facilitate the access to regions within the heart. Forinstance, access to the left atrium of a patient's heart for performingtreatments such as tissue ablation for atrial fibrillation may requirehood 12 to be retroflexed in various configurations to enable sufficientaccess. Thus, the ability to control the steering or articulation ofhood 12 within the patient's heart may facilitate tissue visualizationand treatment.

FIG. 11A shows a variation of the tissue visualization catheter with anexample of steering features. As shown in FIG. 11A, one variation of thevisualization catheter may comprise a tubular member such as anextrusion 206 (which may define a multi-lumen extrusion) and a steerablesegment 202 distal to extrusion 206 with hood 210 coupled to andextending distally from the steerable segment 202. An imaging element212 is also found in hood 210 where the imaging element can be a CMOS orCCD camera with light source, as described above. The imaging element212 can also be a high resolution optical fiber scope (with lightsource) positioned in one of the channels of the multi-lumen extrusion206. The visualization catheter may be further translated along a singlelumen catheter sheath 208 that allows the visualization catheter toretract into or be deployed from the catheter sheath 208. The steerablesegment 202 of the catheter may be also coated with a thin liner 204 toensure the surface of the steerable segment remains smooth andatraumatic to surrounding tissues.

Further details of such a visualization catheter and methods of use areshown and described in U.S. Pat. Pub. 2006/0184048 A1, which isincorporated herein by reference in its entirety.

FIG. 11B and FIG. 11C illustrates an example of the visualizationcatheter being steered by a pull wire mechanism. A pull wire 216 passingthrough extrusion 206 and steerable segment 202 may be terminated atdistal section 214 of steerable segment 202. The proximal end of pullwire 216 may be routed into a handle at the proximal end of extrusion206. As shown in FIG. 11C, the steerable segment 202 is steered into acurved configuration when the pull wire 216 is tensioned from itsproximal end. The interaction between the tensioning and the bending ofsteerable segment 202 of the catheter enables the hood 210 to articulateacross a range of angles. The pull wire 216 can be made from stainlesssteel, nitinol, elgiloy, tungsten, etc.

Shown in FIG. 11D, by combining torquing of the visualization catheterabout the longitudinal axis of the extrusion, hood 210 may be rotated invarious directions 218 and 220 to access more areas with the steeringsegment 202.

FIG. 12A shows a similar embodiment with a double pull wire mechanism tosteer the tissue visualization catheter into a double-bendconfiguration. As shown, a first pull wire 213 may be terminated at afirst location 214 along the steerable segment 202 proximal to hood 210while a second pull wire 221 may be terminated at a second location 222along steerable segment 202 proximal to the first location 214. Thefirst and second locations 214, 222 may both be located along segment202 so long as they are staggered with respect to one another. Moreover,they may terminate along opposite angles of segment 202 to provideopposing bending moments, as described further below. When second pullwire 221 is tensioned, as shown FIG. 12B, hood 210 and segment 202 maybe curved in a first direction with respect to a longitudinal axis ofthe sheath. First pull wire 213 may also be tensioned (before, after, orsimultaneously with second pull wire 221) such that steerable segment202 is articulated into a double-bend configuration, as shown in FIG.12C, where a first curve 224 (defined as Curve A) is curved in anopposite direction from second curve 226 (defined as Curve B). Althoughhood 210 is illustrated in a perpendicular angle relative to the sheath,the degree of tensioning of pull wires 213, 221 may be varied to resultin a variable angle which hood 210 may be configured.

FIG. 12D illustrates the articulated deployment catheter of FIG. 12Cpositioned within a body lumen where hood 210 is accessing a targettissue along a relatively narrow region. To access the target tissue,first curve 224 and second curve 226 may be actuated to position hood210 in a perpendicular configuration relative to the sheath. Theproximal portion of the deployment catheter and the sheath may bemaintained a distance 228 from a surface of the tissue to be visualizedand/or treated while the dual-curved configuration also allows segment202 to maintain a gentle bend radius throughout even if a relativelytight perpendicular bend is attained.

FIG. 13A shows another variation of the steerable tissue visualizationcatheter with 2 pairs of pull wires terminated distally and proximallyalong steerable segment 202 of the catheter. First pull wire 213 andsecond pull wire 221 may be positioned and terminated as above, andthird pull wire 215 may extend distally along segment 202 to terminateat third location 230 proximal to hood 210 and adjacent to firstlocation 214 along an opposing side of segment 202 relative to firstlocation 214. Fourth pull wire 223 may extend along segment 202 andterminate at fourth location 232 which is adjacent to second location222 along an opposing side of segment 202.

First pull wire 213 and second pull wire 221 may be tensioned toarticulate segment 202 and hood 210 in a configuration where first curve224 and second curve 226 are aligned in opposing directions, as aboveand as shown in FIG. 13B. Third and fourth pull wires 215 and 223 mayremain slack during this articulation. However, rather than torquingsegment 202 and hood 210 around to reposition hood 210 along an oppositeside, first and second pull wires 213 and 221 may be released and thirdand fourth pull wires 215 and 223 may be tensioned to articulate hood210 in an opposing direction, as illustrated in FIG. 13C. Alternatively,in actuating pull wires located along a common side of segment 202,e.g., third pull wire 215 and second pull wire 221 as shown in FIG. 13D,segment 202 may be articulated to fully retroflex hood 210 proximallyrelative to a longitudinal axis of the deployment catheter. Althoughfour separate pull wires are illustrated, fewer than or greater thanfour pull wires may be utilized and positioned along segment 202depending upon the desired degree of articulation.

The pullwire mechanism can also interact to produce push steeringmotions as shown in FIGS. 13E and 13F where hood 210 may be placedagainst the tissue surface to be visualized and/or treated and the pullwires may be tensioned in a manner to push or urge hood 210 into directintimate contact against the tissue surface. This can be achieved, forinstance, by tensioning the appropriate pull wires to articulate hood210 in a perpendicular angle, as described above and as shown in theside view of FIG. 13E. With hood 210 initially positioned along thetissue surface to be visualized and/or treated, pull wires 213, 221 maybe tensioned and locked in place, as shown in FIG. 13G. The pushingmotion of hood 210 can be defined as the reduction of first curve 224while the steerable segment 202 remains rigid in a double bendconfiguration.

FIGS. 14A to 14E illustrate another variation of a pull wire mechanismwhere multiple pull wires, four in this instance, are attached at adistal location 238 of steerable segment 250 proximal to hood 210. Thepullwires may be positioned around a segment 250 uniformly spaced apartfrom one another. Thus, first pull wire 240, second pull wire 242, thirdpull wire 244, and fourth pull wire 246 may be aligned parallel toanother and terminate at a common location 238 such that tensioning eachof the pull wires allows for segment 250 and hood 210 to be articulatedaccordingly. With each pull wire relaxed, as shown in FIG. 14A, hood 210may extend distally while tensioning second and or fourth pull wires 242and 246 may articulate hood 210 to curve appropriately, as shown in FIG.14B. Likewise, tensioning first and/or third pull wires 240 and 244 mayarticulate hood 210 in a second direction, as shown in FIG. 14C andtensioning of second and/or third pull wires 242 and 244 or tensioningof first and/or fourth pull wires 240 and 246 may articulate hood 210accordingly, as shown in FIGS. 14D and 14E. Various combinations oftensioning various pull wires may accordingly effect any number ofconfigurations for hood 210.

Turning now to the articulatable segments, various types of links may beutilized to affect a corresponding articulation. For example, FIG. 15Ashows a perspective view of a variation of the tissue visualizationcatheter where the steerable segment may utilize serially alignedmultiple links which collectively facilitate hood articulation. Thisparticular variation illustrates the use of contoured links 252, e.g.,“bump” links as shown in the perspective view of FIG. 15B, which definea distal curved surface 254, e.g., convex in shaped, and a proximalcurved surface 256, e.g., concave in shape, such that when seriallyaligned with a similar link, the curved convex distal surface 254 of onelink mates correspondingly with the curved concave proximal surface 256of the adjacent link and allows the relative pivoting or rocking betweenthe adjacent links along a defined plane, as shown in the detail sideview of FIG. 15C.

Each of the links 252 may define one or more channels 258 therethroughsuch that when a plurality of links 252 are aligned and mated to oneanother, each individual channel 258 forms a continuous lumen throughthe segment. A lining 262, such as an elastic heat shrink polymer, maybe coated upon the link segments to ensure a smooth surface along thelinks. Moreover, the links can be made from materials such as stainlesssteel, PEEK, hard plastics, etc., and manufactured through machining,molding, metal injection molding, etc.

FIGS. 15D to 15F illustrate side views of the serially aligned link 252in a straightened configuration, as shown in FIG. 15D, as well asarticulated in a compound curve, as shown in FIG. 15E, or a singlecurve, as shown in FIG. 15F, where each link is illustrated as pivotingor rocking with respect to an adjacent link. Additionally, once theterminal extent of the relative pivoting or angling between adjacentlinks is reached, the extent of the curvature is reached as well, asshown in the figures.

FIG. 16A shows another variation of links which may be utilized forfacilitating the articulation of segment 202. In this example, ratherthan utilizing contoured “bump” links, pinned links 264 may be utilized.FIG. 16B illustrates detail side views of pinned links 264, each ofwhich may form a proximal and distal recessed surface with anintersecting interface 270 extending axially from both sides of anindividual link 264. This interface 270 may extend and overlap with anadjacent link such that the overlapping interfaces may be aligned andpivotably connected to one another via a pin 266. Rather sliding alongcurved interface surfaces, pinned links 264 may pivot about the axis ofthe pins 266 to collectively form a segment 202 which is constrained toarticulate in a single preset plane. Similar to contoured links, pinnedlinks 264 may define one or more continuous lumens. Moreover, pinnedlinks 264 may be steerable via any of the pullwire mechanisms describedabove.

Additionally, pin linked steerable segments 264 may provide bettercontrol in the movement of the links as compared to other contouredlinks as pin links are constrained to pivot about a secured pointinstead of sliding along curve intersections. In addition, with pins 266securing each adjacent link 264, compound curves created by thesteerable segment 202 may be relatively more rigid which in turn mayprovide a more secure platform for force transmission when utilizinginstruments positioned therethrough. Moreover, pinned links 264 may alsobe utilized for constructing steerable introducer sheaths.

FIG. 17A shows yet another variation of the steerable segment 202comprised of ring links 272. As shown in the detail perspective views ofFIG. 17B, circular ring links 272 may be comprised of a tubular memberdefining an opening therethrough. A distal edge 274 of link 272 may bechamfered such that this chamfered edge 274 is slidingly received in theproximal opening of an adjacent link. Because adjacent links 272 mayslide freely with respect to one another, various angles andconfigurations may be formed. Circular ring links 272 may form complexrigid bends when pull wires are simultaneously tensioned. Otherconfigurations that are not depicted are also possible with any of thelink various combined in alternate configurations. The ring linkembodiment can also be utilized as part of the introducer sheath toproduce steerable sheaths. Similar to contoured links and pinned links,ring links can be made from materials such as, but not limited to,stainless steel, PEEK, hard plastics, etc. Moreover, rings links can bemanufactured through machining, molding, metal injection molding, etc.

In addition, simultaneously tensioning all pull wires threaded alongring links 272 will compress each ring tightly towards each another toform a rigid segment. The rigid segment formed by the tensioned ringlinks may therefore “memorize” the current path taken by the catheter orsheath 276 and hold the catheter or sheath along this set trajectory toprovide for effective force transmission for tools deployed through thecatheter.

FIG. 18 shows a side view of another variation of a steerable segment278 made from a cut tube, e.g., a laser-cut tube, having one or morepull wires therethrough. The laser cut tube 278 can be made frommaterials as described above and cut such that structural spines areformed along the outer bend radius of the steerable segment 278 toprovide a more stable curved platform. A combination of differentpositions of such structural spines may yield steerable segments havinga combination of different bend directions and/or bend radius.

FIG. 19 shows a side and perspective view of another steerable segment202 that comprises a ribbed spine, e.g., a “fish bone” configuration. Acontinuous spine 280 may provide overall cohesive structural strength tothe segment with ribbed extensions 282 extending perpendicularly fromthe spine 280 with gaps 284 formed at regular intervals between theextensions 282 to provide for flexibility of the segment. One or morepull wires 286 may extend through the segment through the ribbedextensions 282, as illustrated in the perspective detail view of FIG.19B. Moreover, the ribbed extensions 282 can be arranged at differentangles about the central longitudinal axis of the deployment catheter toyield steering along different predefined directions.

In yet another variation, the steerable segment 202 may comprise anextrusion having a plurality of slits or cuts 288 made along one or bothsides of the segment 202 such that the slits 288 facilitate the bendingof segment 202, as shown in the perspective and side views of FIGS. 20Aand 20B. The resulting segment 202 results in the slits or cuts 288formed along the inner radius of a desired direction of bend. Hence,when pull wires are tensioned through segment 202, the steerable segment202 may bend in the direction of the slit patterns when the pullwiresare pulled. FIG. 20C illustrates a detail side view of slits 288 showingthe removed portion of material along segment 202. Aside from slits orcuts, grooves, channels, or any other mechanism for the uniform removalof material along segment 202 may be utilized. In another variation,pull tubes will small outer diameter then thin wall thickness can beused in place of pullwires. In this variation, the pull tubes thatsteers the steerable segment can double up as a narrow work channellumen for works such as guidewires or fiberscopes.

FIGS. 21A and 21B show perspective and side views of another variationutilizing an extrusion comprised of two or more sections havingdifferent durometer values and/or material utilized as a steerablesection. The example illustrates a variation having two sections, afirst section 290 having a first durometer and a second section 292having a second durometer which has a relatively higher durometer valuethan first section 290. This variation may accordingly produce aflexible segment that when articulated utilizing any of the mechanismsdescribed herein has a relatively stiffer second section 292 and arelatively more flexible first section 290. The segment 202 may beextruded into a continuous segment or individual segments may beextruded separately and joined together at a joint 275. Moreover, thesegment may be extruded such that the durometer value gradually declinesthe farther distal along the segment. Alternatively, the second section292 may be configured to have a lower durometer value than the firstsection 290.

Aside from articulatable segments along the deployment catheter forpositioning the hood relative to the tissue, other variations mayarticulate the hood assembly by utilizing a combination of theintroducer sheath 294 and deployment catheter 276. As previouslymentioned, a portion of the sheath itself, e.g., a distal portion, mayalso incorporate an articulatable section 298 which may be eitherpre-bent or actively steered depending upon the desired results. Thus,compound curve articulation can be made through active steering of bothsheath and deployment catheter and/or passive steering of both or eithersheath and deployment catheter.

FIG. 22A shows a side view of a visualization assembly 210 having theactively articulated double-bend steering described above along with asheath 294 having an articulatable distal segment 298. In this example,distal segment 298 is illustrated as being pre-bent such that when thedistal segment 298 is unconstrained, segment 298 relaxes into a pre-bentconfiguration as shown. Thus when deployed, hood 210 may be articulatedinto position relative to the tissue surface via at least three curvableor curved sections, e.g., first curve 224 (Curve A), second curve 226(Curve B), and third curve 302 defined by the distal segment 298 ofsheath 294 (Curve C). By varying the tension and/or articulation betweeneach of the curves, hood 210 may be positioned in a variety ofconfigurations and angles. Additionally, the deployment catheter may betranslated and/or rotated, as shown by directional indication 296 abouta longitudinal axis of the catheter relative to sheath 294 to furtherprovide additional degrees-of-freedom.

Rather than utilizing the double-bend system, a single curve along thesegment 202 may be utilized with the sheath 294. As illustrated in theside view of FIG. 22B, a single curve, e.g., second curve 226 may bearticulated when advanced distally of distal segment 298 of sheath 294such that the second curve 226 is articulated in a direction oppositionto the curvature of distal segment 298. Alternatively, second curve 226may be articulated to curve in the same direction as the curvature ofthird curve 302 such that hood 210 is retroflexed proximally relative tosheath 294, as illustrated in FIG. 22C.

By utilizing one or all curves available through the combination of thedeployment catheter with the sheath, the assembly may be used to accessany region within a body lumen. For instance, FIG. 22D illustrates apartial cross-sectional view of hood assembly 210 advancedintravascularly through the inferior vena cava IVC and into the rightatrium RA of a patient's heart. Segment 202 may be initially directed bythird curve 302 of sheath 294 towards a region of tissue to be examinedand/or treated. By rotating sheath 294 relative to the right atrium RA,an initial trajectory of hood 210 as well as articulatable segment 202may be effectively directed. As hood 210 is deployed, first 224, second226, and third curves 294 may be configured desirably to direct hood 210towards a tissue region such as the atrial septum AS, e.g., forpotentially accessing the left atrium LA of the heart, as shown in FIG.22E. As further illustrated in FIG. 22F, hood 210 and segment 202 may berotated relative to sheath 294 to redirect or reposition hood 210 onanother region of tissue.

FIG. 23A shows another variation of the steering system utilizing asteerable or pre-bent sheath 294 in combination with a pre-bent catheter304 which may be straightened when constrained for intravasculardelivery but free to reconfigure into a pre-bent shape with a firstcurve 224 when unconstrained. As shown in FIG. 23B, catheter 304 may beadvanced through sheath 294 until hood 210 is deployed and cathetercurve 224 is unconstrained by sheath 294. The example of FIG. 23B showshow first curve 224 of deployment catheter 304 may be aligned with thirdcurve 302 of distal segment 298 within the same plane and same directionto retroflex hood 210 relative to sheath 294. Alternatively, catheter304 may be torqued or initially advanced from sheath 294 such that firstcurve 224 is aligned in an opposite direction from third curve 302, asshown in FIG. 23C. Additionally, deployment catheter 304 may be torquedor initially advanced from sheath 294 such that first curve 224 isaligned in a non-planar configuration, e.g., perpendicularly, relativeto third curve 302, as shown in FIG. 23D. Although specific directionsand angles may be shown, these are intended to be illustrative and anyvarious combinations of angles and configurations may be performed bythe assembly.

FIG. 24A shows a side view of yet another variation utilizing a sheath294 having a steerable or pre-bent segment 298 in combination with adeployment catheter 276 having an actively steered segment which mayarticulate hood 210 at an angle Φ relative to a longitudinal axis 275 ofthe deployment catheter 276. In this configuration, segment 298 ofsheath 294 may provide the initial trajectory, as indicated by angle Ψrelative to a longitudinal axis 295 of sheath 294. In use, after sheath294 and segment 298 has been advanced into an initial position, e.g.,transseptally through the atrial septum AS and within the left atrium LAof a patient's heart as shown in FIG. 24B, the general trajectory angleΨ may be defined by segment 298 of sheath 294 such that deploymentcatheter 276, once advanced distally of sheath 294, is directedgenerally towards the targeted tissue region such as the pulmonary veinostia 310. With hood 210 deployed and positioned generally over thetargeted tissue region, the steerable segment of deployment catheter 276may be articulated, e.g., at an angle Φ, to further direct hood 210 uponthe targeted tissue. The combination of general steering (or coursesteering) of sheath 294 with the articulation (or fine steering) ofdeployment catheter 276 may be utilized to effectively articulate hood210 upon any desired region of tissue. Moreover, navigation may beeffective when angle Ψ>Φ, although this is not necessary to effectivelyarticulate hood 210.

Aside from steering in the deployment catheter and/or sheath, variousalternatives may also incorporate steerable hood features eitherindependently or in various combinations with any of the catheter and/orsheath articulation mechanisms described herein. An example isillustrated in the perspective views of FIGS. 25A and 25B which show asteerable hood 210 having one or more steerable members or leaflets 312,which may also function to provide structural support to the deployedhood 210. Each member or leaflet 312 may be integrated with the hood 210material or overlaid atop and otherwise attached to hood 210. Member orleaflet 312 are illustrated as closed looped members which extenddistally over hood 210, but other atraumatic configurations may beemployed. A proximal end of one or more leaflets 312 may extendproximally through deployment catheter 276 such that a user maymanipulate the leaflets 312 by pulling and/or pushing the leaflet 312proximal end to effect a corresponding result along hood 210. Asillustrated in FIG. 25B, upon pulling a proximal end of one leaflet 312,hood 210 may be slanted to an angle Φ, which may be defined as the anglebetween an axis 311 transverse to deployment catheter 276 and an axis313 transverse to hood 210. By pulling/pushing one or more leafletstruts simultaneously, the hood 210 can be steered and slanted alongdifferent planes. Such leaflet struts 312 can be made from variousmaterials, e.g., nitinol, stainless steel, tungsten, elgiloy, etc.

FIG. 25C shows a side view of steerable hood 210 directed against atissue surface 316 for visualization and/or treatment. As describedabove, sheath 294 may be steered to provide a general trajectory and anangle Ψ to direct the deployment catheter 276 generally towards thetarget tissue surface 316. Once deployed hood 210 has been brought intoproximity, the leaflet struts 312 may be actuated to slant or tilt hood210 at an angle Φ such that the distal end of hood 210 may be placeddirectly in apposition against the tissue surface 316 to facilitatesealing, visualization, and tissue treatment.

FIGS. 26A and 26B show perspective and side views, respectively, ofanother variation of a steerable hood 210 which utilizes a pair ofstruts 320, 321 which may be positioned along the walls of hood 210 andare connected to a circumferential member 318 providing support to thedistal circumferential edge of hood 210. Similarly to the leaflet strutsabove, the steering struts 320, 321 may be pulled and/or pushedalternately to slant hood 210 at a desired angle.

In yet another embodiment, articulation of hood 210 may be affectedpassively by having a conformable lip 322 positioned to extend distallyabout a circumference of hood 210, as shown in the perspective view ofFIG. 27A. The conformable lip 322 can be made from an inflatable balloonshaped into a donut or toroidal shape defining a passage 321therethrough and attached to the distal end of hood 210. The balloon canbe (but is not limited to) materials such as polyurethane, silicone,rubber latex, PET (polyethylene terephthalate), etc. The conformable lip322 can also be made from an extrusion of soft conformable materialssuch as polyether/polyester sponges or polystyrene (Styrofoam) and mayalso be transparent.

In use, as hood 210 is advanced towards the targeted tissue region, asshown in FIG. 27B, conformable lip 322 may be inflated or otherwiseexpanded. As the hood 210 is pressed (possibly at an angle) againsttarget tissue, as indicated in FIG. 27C, conformable lip 322 may deformagainst the anatomy of the tissue surface to facilitate sealing andvisualization.

Turning now to the perspective assembly view of FIG. 28, anothervariation of an articulatable deployment catheter 276 is shown whichcomprises a distal steerable section 324 and a proximal steerablesection 326 located proximally of the distal steerable section 324. Anintervening link 347 may couple the sections 324, 326 to one another andprovide a terminal link to which one or more pull wires may be attachedin controlling one or both sections. The distal steerable section 324may utilize individual links 340 which allow for the section 324 to bearticulated in a variety of different directions and angles, e.g.,four-way steering, to enable omni-direction articulation. The individuallinks 340 may accordingly utilize a body member 341 having a pair ofyoke members 343 positioned opposite to one another and extendingdistally from the body member 341 and each defining an opening. A pairof pins 345 may each extend radially in opposing directions from bodymember 341 and in a perpendicular plane relative to a plane defined bythe yoke members 343.

Turning to the perspective assembly view of FIG. 29A, the pins 345 ofeach link 340 may be pivotably received by the yoke members 343 of anadjacent link 340 such that the pins 345 and yoke members 343 are joinedin an alternating manner. This alternating connection allows for theserially aligned links 340 to be articulated omni-directionally.

The links 328 of the proximal steering section 326 may be seen in detailin the perspective view of FIG. 28. These links 328 may also comprise apair of yoke members 331 positioned opposite to one another andextending distally from body member 329. However, the pins 333 mayextend radially in opposing directions while remaining in the same planeas that defined by yoke members 331. When joined together in series, asillustrated in the perspective detail view of FIG. 29B, each pin 333 ofeach link 328 may be pivotably received by the yoke members 331 of anadjacent link 328. Yet when joined, the composite proximal steeringsection 326 may be constrained to bend planarly within a single planerelative to the rest of the deployment catheter.

The combined distal steerable section 324 and a proximal steerablesection 326 results in a proximal steering section which can bearticulated in a single plane to retroflex the entire distal assemblyand a distal steering section which can then be articulated any numberof directions, e.g., four-way steering, to access anatomical structureswithin the heart or any other lumen. The assembly may thus be used,e.g., to create circumferential lesions around the ostia of thepulmonary veins in the left atrium while the underlying tissue remainsunder direct visualization through the hood.

The operator may manipulate catheter 276 to position hood 210 on oraround the ostia of the pulmonary veins in the left atrium LA. Once theaccurate positioning of catheter 276 has been verified by real-timeimages captured through the imaging hood 210, as described above,ablation through any number of instruments may be accomplished. Asillustrated in the partial cross-sectional view of FIG. 30A, deploymentcatheter 276 is shown advanced transseptally across the atrial septum ASand into the left atrium LA. To access the ostia of the pulmonary veins,such as the left superior pulmonary vein ostium 342, proximal steeringsection 326 may be articulated to first retroflex the distal assembly tobring hood 210 into proximity with ostium 342. Distal steering section324 may then be articulated to bring hood 210 into contact against thetissue surface. Once the appropriate location has been determinedvisually, as described above, the underlying tissue may be ablated 344.As the entire circumference of ostium 342 is desirably ablated toadequately treat conditions such as atrial fibrillation, distal steeringsection 324 may be articulated to move hood 210 about the entire ostium342 while ablating the tissue due to the omni-directional steeringcapability of steering section 324 while the curvature of proximalsteering section 326 may be maintained, as shown in FIGS. 30B and 30C.

Once the ablation about a first ostium is completed, deployment catheter276 may be repositioned by manipulating the catheter and/or adjustingthe articulation of proximal steering section 326, as illustrated inFIG. 30D. Once hood 210 has been repositioned, e.g., proximate to theleft superior pulmonary vein ostium 346, the process may be repeated andthe underlying tissue may be ablated 348 about the ostium 346 whileutilizing the steering capabilities of both steering sections 324, 326,as shown in the FIGS. 30E and 30F.

The applications of the disclosed invention discussed above are notlimited to certain treatments or regions of the body, but may includeany number of other treatments and areas of the body. Modification ofthe above-described methods and devices for carrying out the invention,and variations of aspects of the invention that are obvious to those ofskill in the arts are intended to be within the scope of thisdisclosure. Moreover, various combinations of aspects between examplesare also contemplated and are considered to be within the scope of thisdisclosure as well.

What is claimed is:
 1. A method of accessing difficult-to-reach targettissue in a region of a body having continuous interfering blood flow,the method comprising: advancing a deployment catheter shaft having anarticulatable assembly near or at a distal portion of the catheter shaftinto the region of the body, the articulatable assembly having aproximal steerable section and a distal steerable section fixedlyconnected, wherein the distal steerable section is positioned distal tothe proximal steerable section; bending the proximal steerable sectionsuch that a hood attached to a distal end of the distal steerablesection is articulated in a first plane relative to a longitudinal axisof the catheter shaft, wherein the hood projects distally from thedistal end of the distal steerable section and defines an open areatherein in fluid communication with an environment distal of a distalopening defined by the hood and further has at least one membraneextending over the distal opening such that the at least one membranepartially covers the open area; bending the distal steerable section inone or more additional planes relative to a longitudinal axis of theproximal steerable section such that the hood is positioned in proximityto the target tissue; bending the hood with respect to the distalsteerable section through use of steerable members integrated with thehood; infusing a fluid through the catheter shaft and into the open areasuch that the infused fluid displaces blood from within the open area toan environment external to the hood through at least one aperturedefined along the hood; and visualizing the target tissue within theopen area through the infused fluid.
 2. The method of claim 1 whereinadvancing comprises advancing the deployment catheter into a heart of apatient.
 3. The method of claim 1 wherein bending the proximal sectioncomprises constraining the proximal section to curve within the firstplane.
 4. The method of claim 1 wherein bending the distal sectioncomprises bending the distal section in a plurality of planes relativeto the longitudinal axis of the catheter.
 5. The method of claim 1further comprising positioning the open area of the hood against oradjacent to the target tissue.
 6. The method of claim 1 wherein infusinga fluid comprises infusing a transparent fluid into the open areadefined by the hood.
 7. The method of claim 1 further comprisingvisualizing the target tissue within the open area through thetransparent fluid via an imager integrated with the deployment cathetershaft.
 8. The method of claim 1 further comprising ablating at least aportion of the target tissue within the open area.
 9. The method ofclaim 8 further comprising ablating tissue circumferentially surroundingan ostium of a pulmonary vein.
 10. The method of claim 1 furthercomprising repositioning the hood relative to the target tissue byre-articulating the distal section.
 11. A method of accessing a targettissue in a chamber of a heart, the method comprising: advancing adeployment catheter shaft having an articulatable assembly near or at adistal portion of the catheter shaft into a region of the body, thearticulatable assembly having a proximal steerable section and a distalsteerable section fixedly connected, the distal steerable section beingpositioned distal to the proximal steerable section and further having ahood projecting distally from the distal steerable section, wherein thehood defines an open area therein in fluid communication with anenvironment distal of a distal opening defined by the hood and furtherhas at least one membrane extending over the distal opening such thatthe at least one membrane partially covers the open area; positioningthe distal steerable section within range of the target tissue bybending the proximal steerable section such that a distal end of thedistal steerable section bends in a first plane relative to alongitudinal axis of the catheter shaft; bending the distal steerablesection in two planes relative to a longitudinal axis of the proximalsteerable section such that the hood is positioned in proximity to thetarget tissue; bending the hood with respect to the distal steerablesection through use of steerable members integrated with the hood;infusing a fluid through the catheter shaft and into the open area suchthat the infused fluid displaces blood from within the open area to anenvironment external to the hood through at least one aperture definedalong the membrane; and visualizing the target tissue through the fluidretained temporarily within the open area.